Methodology for Integrating Mineral-Impregnated Carbon Fibers as Reinforcement in Fine Filament 3D Concrete Printing

Mineral-impregnated carbon fibers (MCF) represent an advanced non-metallic reinforcement material offering high structural efficiency in concrete elements. Carbon fibers are impregnated with a suspension of ultrafine cement and microsilica and processed into rovings, providing high strength, design flexibility, and excellent bonding to concrete. In their freshly impregnated state, MCF exhibit high flexibility and can be deposited in any geometries, making them particularly suitable for complex structures manufactured using innovative processes such as 3D concrete printing (3DCP). Despite many advancements in reinforcement strategies for 3DCP, there is a lack of a simultaneous continuous corrosion-resistant reinforcement strategy. This is to be achieved by directly integrating freshly manufactured, still flexible MCF as longitudinal reinforcement of extruded concrete strands. Various modifications in MCF processing and print head modification are being investigated. This study highlights the potential of freshly impregnated MCF to improve structural continuity and automation due to their high flexibility. After modification, initial mechanical tests are carried out on printed MCF-reinforced concrete strands in comparison to cast speciments. These results are discussed and supplemented by visual findings from computer tomography. Although the mechanical performance of the printed specimens remains inferior to that of the cast specimens, as confirmed by CT analyses, the results demonstrate the feasibility of an effective method for simultaneous and continuous reinforcement of concrete during the 3D printing process.